Magnesium alloys containing magnesium and various additive elements are increasingly employed as materials for housings of mobile electronic devices such as cellular phones and laptop computers, and automobile parts.
Since magnesium alloys have a hexagonal crystalline structure (hexagonal close-packed (hcp) structure) and has low plastic formability at ordinary temperature, magnesium alloy structural members such as the housings described above are mainly formed of cast materials by a die casting method or a thixomolding method. Recently, studies have been made to form the housing by press-forming a sheet composed of an AZ31 alloy according to American Society for Testing and Materials (ASTM) standard. Patent literature 1 proposes a rolled sheet composed of an alloy equivalent to AZ91 alloy of the ASTM standard, the rolled sheet having good press formability.